linux-kernel - [PATCH v2 44/45] KVM: Move putting of vcpu->pid to kvm_vcpu

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Date:   Wed, 18 Dec 2019 13:55:29 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Marc Zyngier <maz@...nel.org>, James Hogan <jhogan@...nel.org>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm-ppc@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kurz <groug@...d.org>
Subject: [PATCH v2 44/45] KVM: Move putting of vcpu->pid to kvm_vcpu_destroy()

Move the putting of vcpu->pid to kvm_vcpu_destroy().  vcpu->pid is
guaranteed to be NULL when kvm_vcpu_uninit() is called in the error path
of kvm_vm_ioctl_create_vcpu(), e.g. it is explicitly nullified by
kvm_vcpu_init() and is only changed by KVM_RUN.

No functional change intended.

Acked-by: Christoffer Dall <christoffer.dall@....com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 virt/kvm/kvm_main.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 21533a472ead..6912d81ca32d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -352,12 +352,6 @@ static int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
 
 static void kvm_vcpu_uninit(struct kvm_vcpu *vcpu)
 {
-	/*
-	 * no need for rcu_read_lock as VCPU_RUN is the only place that
-	 * will change the vcpu->pid pointer and on uninit all file
-	 * descriptors are already gone.
-	 */
-	put_pid(rcu_dereference_protected(vcpu->pid, 1));
 	free_page((unsigned long)vcpu->run);
 }
 
@@ -365,6 +359,13 @@ void kvm_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
 	kvm_arch_vcpu_destroy(vcpu);
 
+	/*
+	 * No need for rcu_read_lock as VCPU_RUN is the only place that changes
+	 * the vcpu->pid pointer, and at destruction time all file descriptors
+	 * are already gone.
+	 */
+	put_pid(rcu_dereference_protected(vcpu->pid, 1));
+
 	kvm_vcpu_uninit(vcpu);
 	kmem_cache_free(kvm_vcpu_cache, vcpu);
 }
-- 
2.24.1